The company is developing a giant reusable rocketship for those missions -- called BFR, or Big Falcon Rocket. Inside the company, it's nicknamed the "Big F--king Rocket." It plans to start building the first one by the middle of next year.

That's the same rocket that Musk says could be used to zoom people from city to city on Earth, traveling as fast as 27,000 kilometers per hour (17,000 mph).

Richard Branson has said he wants to perfect a "rocket plane" to transport people between cities on Earth via space. Branson, who's pursuing his space ambitions through Virgin Galactic, has forecast that the trip from New York to Sydney could one day take 30 minutes.

Musk also has plans to build an underground "hyperloop" network that can shuttle commuters between New York and Washington, which are about 230 miles apart, in 29 minutes.